1. Field of the Invention
The present invention relates to digital image processing, and more particularly, to a method of controlling auto white balance that can accurately display white when a camera of an electric device uses a wide-angle lens that may cause deterioration in image quality and a variation in color distribution due to unnecessary light incident from the surrounding environment.
2. Description of the Related Art
In general, human eyes always perceive the same subject as having the same color under different light sources. That is, even when one light source is switched to another light source, such as sunlight, a fluorescent lamp, and an incandescent lamp, which has a different color temperature, human eyes always see white as white. On the other hand, since an image sensor using a solid-state image capturing device converts light into an electrical signal, the image sensor directly detects colors of the subject that vary according to the light sources. Therefore, most of the digital image processing apparatuses, for example, digital cameras, use algorithms for controlling auto white balance so that the colors detected by the image sensor can be similar to colors perceived by human eyes.
Auto white balance performed in the digital image processing apparatus is generally controlled by representing a subject appearing white with intermediate luminance in an image as color signals (RGB signals) having the same output level. In the related art, the most commonly used algorithm to control auto white balance calculates a mean color value on the assumption that a mean color value of the screen is white regardless of a variation in light source, obtains gains of color signal levels so that the mean color value can be white, and applies the obtained gains to the entire image. For example, in the related art, the method of controlling auto white balance integrates values of Cb and Cr of color signals of pixels in an area supposed to be white in the input image, calculates mean values, and controls gains of red (R) and blue (B). In the related art, the method of controlling auto white balance determines areas supposed to be white for the entire input image by using the same method. Therefore, a digital imaging apparatus, for example, a camera of an electric device, which uses a wide-angle lens in which a relatively considerable amount of light is incident to the edge of the image, has difficulty in exactly displaying colors of the edge of the image, that is, difficulty with precise auto white balance.